Pit & Quarry, July 2017

The many sizes and shapes of containment mean many installations have to deal with obstructions and shapes of containment mean many installations have to deal with obstructions like mechanical bracing for structural support Plant personnel like reliability engineers operations leaders facilities engineers maintenance personnel and others are regularly looking for ways to increase throughput and improve efficiencies Now companies are designing process instrumentation that offers different types of technologies to provide reliable level and point level detection solutions for tough applications TECH EXPLORATION With safety being a priority any basic level measurement must be reliable robust and accurate and there must be robust systems to guard against spillages from overfilling vessels Unfortunately even with todays advancements in process instrumentation there isnt one technology that provides undaunted measurement results in every application The mechanical installation constraints the conditions within the containment and the capabilities of the level device will all affect the choice of measuring device Within the level instrumentation spectrum there are several different technologies but the major technology contenders are ultrasonic TDR guided wave radar and non contact microwave radar When dealing with solids materials in an industrial environment the conditions for measurement are extremely difficult The conditions require a technology that can endure heavy dust undulated material surfaces and sometimes hot conditions with buildup problems on equipment installed in the application If the height of the material containment for level measurement is more than 30 to 40 ft then it is more appropriate and practical to choose a non contact level measurement technology like ultrasonic or microwave radar TDR or guided wave radar can provide continuous level measurements up to 80 ft but the tensile forces and loading on the cable become extreme in solids materials Thus breakage and shearing are possibilities Also as material shifts from one point to another in solids the cable follows that line of movement With level measurement in solids beyond 30 to 40 ft a non contact technology can be a wise choice Choosing between non contact ultrasonic and microwave radar for solids materials can be challenging but there are some simple rules to keep in mind when considering the choice for an application Remember solids come in many different sizes and shapes and regardless of the particle size the material will be very dusty in the airspace The method of fill and removal from the containment will also increase the dust in the airspace causing further deterioration of the measurement technologys signal Using a dense phase pneumatic conveying system during fill essentially blowing the material into the silo from the top the airspace conditions are extremely clouded and difficult for some level technologies to perform reliably In these conditions the transmitted signal must be strong and have the ability to penetrate dust without being attenuated KEYS TO MICROWAVE RADAR With microwave radar the frequency of the device used and the antenna design www kpijci com pitandquarry com July 2017 PIT QUARRY 33